The chemical reaction$K_2SO_4 \text{ (aq.)} + BaCl_2 \text{ (aq.)} \rightarrow 2KCl \text{ (aq.)} + BaSO_4\downarrow \text{ (solid)}$is an example of:

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CDS - 2025

The chemical reaction
$K_2SO_4 \text{ (aq.)} + BaCl_2 \text{ (aq.)} \rightarrow 2KCl \text{ (aq.)} + BaSO_4\downarrow \text{ (solid)}$
is an example of:

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Addition reaction

Displacement reaction

Decomposition reaction

Double displacement reaction

The correct answer is

Double displacement reaction

Double Displacement Reaction: $K_2SO_4$ and $BaCl_2$

The provided chemical reaction is:

$K_2SO_4 \text{ (aq.)} + BaCl_2 \text{ (aq.)} \rightarrow 2KCl \text{ (aq.)} + BaSO_4\downarrow \text{ (solid)}$

Let's analyze this reaction to understand why it is classified as a double displacement reaction.

Understanding the Reaction Mechanism

In this reaction, we start with two ionic compounds dissolved in water:

Potassium sulfate ($K_2SO_4$)
Barium chloride ($BaCl_2$)

When these two aqueous solutions are mixed, the ions present are $K^+$, $SO_4^{2-}$, $Ba^{2+}$, and $Cl^-$. In a double displacement reaction, the positive ions (cations) and negative ions (anions) of the two reactant compounds switch partners.

The cation from the first compound ($K^+$) combines with the anion from the second compound ($Cl^-$).
The cation from the second compound ($Ba^{2+}$) combines with the anion from the first compound ($SO_4^{2-}$).

This results in the formation of two new compounds:

Potassium chloride ($KCl$), which remains dissolved in water (aqueous, aq.).
Barium sulfate ($BaSO_4$), which is insoluble in water and forms a solid precipitate ($\downarrow$, solid).

The overall process involves the exchange of ions: the $K^+$ ions were initially with $SO_4^{2-}$ and the $Ba^{2+}$ ions were with $Cl^-$. After the reaction, $K^+$ ions are with $Cl^-$ and $Ba^{2+}$ ions are with $SO_4^{2-}$. This characteristic exchange defines it as a double displacement reaction.

Comparing with Other Reaction Types

Let's see why the other options are not suitable:

Addition reaction: In an addition reaction, two or more simple substances combine to form a single, more complex product. This reaction produces two products ($KCl$ and $BaSO_4$), so it is not an addition reaction.
Displacement reaction: A displacement reaction typically involves a more reactive element displacing a less reactive element from its compound (e.g., $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$). In this reaction, ions are swapping places, not a single element displacing another.
Decomposition reaction: A decomposition reaction occurs when a single compound breaks down into two or more simpler substances (e.g., $CaCO_3 \rightarrow CaO + CO_2$). This reaction involves two reactants combining and rearranging, not breaking down.
Double displacement reaction: This perfectly describes the reaction where the ions $K^+$ and $Ba^{2+}$ switch their respective partners $SO_4^{2-}$ and $Cl^-$, leading to the formation of new compounds, one of which is a precipitate.

Conclusion

The reaction $K_2SO_4 \text{ (aq.)} + BaCl_2 \text{ (aq.)} \rightarrow 2KCl \text{ (aq.)} + BaSO_4\downarrow \text{ (solid)}$ is a clear example of a double displacement reaction because the cations ($K^+$ and $Ba^{2+}$) and anions ($SO_4^{2-}$ and $Cl^-$) exchange partners between the two reacting ionic compounds.

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